Rough operation?
 

Ok so I started up my car(77 280z) this morning and it's was idling kind of rough but it always does that. But it carries the roughness all the way through 4k, which it never did. And it backfires now. I checked my wires and they seem fine. I looked at my dizzy cap and I didn't see a crack but I didn't look that hard. I checked my EGR and the plenum flapped up and down fine. Any idea's on what it is? Thanks

rough running
 

ya i had that same thing happen to my 78 and if i tried to drive it the dang thing would die before the clutch was even all the way engaged then one day she wouldnt start at all i replaced the cap and rotor which both still looked okay only a minor amount of pitting on the cap contacts she fired right up also replaced my plugs later they where a little fouled. also did this start after a cold period in the weather thats when mine did it i think my cold start valve is bad hope this helps

Sounds like you have either an ignition miss or bad injector. You need to do some trouble shooting to figure out what cylinder(s) are to blame. Let it idle, get a spark plug boot puller and gently pull off the number one wire slightly from the plug and see if the miss gets worse or is unchanged. Replace plug wire on plug and move to next cylinder. Do this to all cylinders to narrow down which cylinders are missing. This way you can make sure there is spark getting to these cylinders as well. When you get it narrowed down by cylinder, pull the plug and inspect it. If its wet and black, good sign the plug is bad. If its dry as a bone, probably not getting any fuel. Also a good idea to have the compression of the missing cylinder(s) checked when you've got it narrowed down to see if its a miss due to low compression. Hope this helps! Good luck.